This invention relates to extracorporeal liquid circuits. Hemodialysis removes toxic substances and metabolic wastes from the bloodstream using an extracorporeal circuit with components designed to perform ultrafiltration and diffusion on the blood. Before the blood is returned to the body, air bubbles are removed from the blood to prevent embolisms.
Referring to FIG. 1, a typical extracorporeal circuit 100 includes tubing through which the blood flows and components for filtering and performing dialysis on the blood. Blood flows from a patient 105 through arterial tubing 110. Blood drips into a drip chamber 115 where a connecting tube from the drip chamber 115 attaches to a sensor 125 on a hemodialysis machine that determines the pressure of the blood on the arterial side of the circuit 100. A pump 120 forces the blood to continue along the path through the circuit 100. A dialyzer 130 separates waste products from the blood.
After passing through the dialyzer 130, the blood flows through venous tubing 140 into a second drip chamber 150. The drip chamber 150 can function as an air trap. Free gases in the blood may be able to escape into the drip chamber 150 before the blood continues to the patient. A sensor 170 is in communication with air in the drip chamber through tube 165. The sensor 170 can determine the pressure on the venous side of the circuit 100.
Heparin or drugs 160 can be added to the blood in the drip chamber 115. When blood is exposed to oxygen, the blood begins to clot. The drip chamber 150 may include a filter for preventing any clots from exiting the drip chamber 150 and entering the patient 105. The blood continues from the drip chamber through venous tubing 180 and through a bubble detector 175 before returning to the patient 105.
In addition to preventing clotting, air needs to be kept out of the venous line to prevent injecting air into the patient during treatment, which could result into air embolism.